Highly contoured, multi-leg structures having high strength and lightweight may be used in various applications, such as in aerospace vehicles. A variety of frames and similar structures used in aerospace applications may have legs which are highly curved or contoured along the length of the structure. For example, hoop shaped frame sections for an aircraft fuselage may be formed from two separate pieces, comprising a C-shaped channel and an L-shaped member jointed together with fasteners. The L-shaped channel acts as a shear tie to which an outer skin of the aircraft is fastened.
The two-piece frame described above requires assembly, separate pieces of tooling and separate inspection processes. Moreover, laminate ply layout is performed using a moving Cartesian coordinate reference which complicates the task of tailoring the laminated plies of the frame to meet various performance requirements, including strength, rigidity and weight. Also, two-piece frames are also relatively expensive to fabricate because of the hand labor needed to assemble the pieces, and additional material requirements, including multiple fasteners.
Accordingly, there is a need for a structural frame for aircraft fuselage applications which reduces weight, material and labor, while meeting the necessary specification for aircraft applications. There is also a need for a high performance structural frame that is suitable for fabrication in a high volume production environment.